Compressed gas such as air is often used for starting an aircraft gas turbine, or jet engine. Compressed air flows to the starter which causes rotation of the compressors and the turbines within the jet engine. When sufficient air flows through the jet engine (reflected by turbine speed or otherwise), the jet fuel can be ignited within the combustion area/combustor to start the engine. Without the compressor/turbine rotation provided by the starter, fuel combustion and air flow through the engine will not be sufficient to start the engine. The compressed air from the air turbine starter is controlled by a starter valve, such as an air regulating and shut-off butterfly valve, and the starter valve is, in turn, controlled by a control valve.
Typically, the control valve is coupled to a probe that is disposed within the same duct within which the starter valve resides. The probe is configured to divert a portion of air that flows through the duct toward the control valve so that the control valve may be pneumatically operated.
At times, the air that flows through the starter valve duct may contain various particles, dirt, or other contaminants. When the air is directed to various parts of the control valve, such as for example, the orifices, valve mechanism, or springs, particles in the air may buildup or collect on the components, thereby possibly decreasing operability and increasing frequency of maintenance. To prevent or minimize particle contamination, filters have been used downstream of the probe or mounted within the probe. The most common method for filtering has been the use of porous filters, such as those consisting of wire mesh or sintered powdered metal, embedded within the probe. However, porous filters have limited life due to pore clogging and thus necessitate frequent removal and replacement of the probe. Other types of filters have included down-stream facing filters. Although these types of filters do not need frequent replacement, they are not highly effective filters.
Accordingly, there exists a need for a filter with improved filtering capabilities. Preferably, the filter operates with or is an integral part of the probe. Additionally, it is desirable that the improved filter be low in cost to manufacture and does not need frequent replacement. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.